Pneumatic devices for driving fasteners or like purposes



M. E. HlLLIER PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES l0 Sheets-Sheet 1 Filed Dec. 20, 1966 F 1$ w E,

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PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES Filed Dec. 20, 1956 10 Sheets-Sheet 2 1? 273A 175 4 7F170 I76 IN VE N TOR ZMCQZfJZ/W Z2 15 /44 //z Nov. 25, m9 M. E. HILLIER 3,479,926

PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES Filed Dec. 20, 1966 10 Sheets-Sheet 5 NW 9 119 59 5%. E. HILLIER 3,479,925

PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES Filed Dec. 20, 1966 10 Sheets-Sheet 4 xxx INVENTOA jyqzmz/w 55 /4 4 M. E. HILLIEIR 3,479,926

PNEUMATIC, DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES New. 25, E969 l0 Sheets-Sheet 5 Filed Dec. 20, 1966 4 a x M X X X X a Z 3 C 0.! 3 0. 2

INVENTOI? J ZQZ (4.0% 1 974 .4 15x Nov. 25, 1969 M. E. HILLIER 3,479,926

PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES ,wvavTw? M44 601/ 27m 4 my? NW. 25, m9 M. E. MILLER I 3,479,926

PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES Filed Dec. 20. 1966 l0 Sheets-Sheet 7 M. E. HILLKER ZMQW. 25,, HQQQ PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES l0 Sheets-Sheet 8 Filed Dec. 20, 1966 iii INVENTOR flf zmmv 5719744/52 M. E. HILLIER PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES 10 Sheets-Sheet 9 Filed Dec.

NQN MEN Em FQQN @QN MEN M. E. HILLBER PNEUPZATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPOSES Filed Dec. 20, 1966 l0 Sheets-Sheet l0 INVE/VTQR United States Patent 3,479,926 PNEUMATIC DEVICES FOR DRIVING FASTENERS OR LIKE PURPUSES Malcolm Edwin Hillier, Upper Walmer, Deal, Kent, England, assignor to Gaston E. Marbaix Limited, a British company Filed Dec. 20, 1966, Ser. No. 603,256 Claims priority, application Great Britain, Dec. 29, 1965, 55,142/ 65 lint. Cl. F15!) 13/04; F16 11/04; 1325c 5/06 US. Cl. 91-404 31 Claims ABSTRACT OF THE DISCLOSURE This invention involves a pneumatic gun or the like having a pair of main valve members at opposite ends of a main cylinder in which a double-acting main piston operates such that the movement of the working piston controls the valve members involved in the working phase of the cycle and the first-mentioned valve is provided with means for enabling venting in the return phase.

This invention relates to pneumatic power devices for driving fasteners and like purposes, such as are sometimes called pneumatic guns or air guns (the latter not to be confused with the air gun type of Weapon). Such devices are, broadly speaking, percussive tools and may With suitable adaptation be used as hammers, riveters and for kindred purposes.

The invention seeks to provide a robust and economic tool of this kind, which for a given power and length of working stroke can be more compact than known tools, in which the speed of the operative part may be increased as compared with known practice, and which is such that I a considerable proportion of the working parts may be made of synthetic plastic.

One of the important factors in such tools is the provision of a large port-area opening very quickly, for the working air, and various valve arrangements have been proposed to that end. The invention provides simple and effective valve arrangements. It also affords a construction in which the mass and therefore the inertia of the working part is kept small; and in which simple and effective control for the required return stroke is afforded.

In air guns of the kind to which the invention relates, it has been proposed to achieve a large and sudden valve opening for the air for the working stroke, by providing an admission valve which was virtually the whole head of the cylinder, seating on the upper rim of the cylinder.

Various return-stroke expedients have been used, ranging from return springs to the use of differential piston areas. The known air guns have a considerable overall length in order to accommodate the required actions, and a secondary disadvantage of this was the accompanying weight. Most of the tools known are hand-held, so that weight is quite an important factor.

Examples of the prior art above indicated are to be seen in US. specification No. 2,979,725 and the other specifications therein referred to, and corresponding United Kingdom specification No. 929,341.

Another advantage which can be achieved in some forms of the invention, is that one piston-valve element can be arranged to open before the other, so that venting of air from below the working piston is achieved in a phase which precedes the working stroke, with the result that the working stroke-unimpeded by air trapped below the working piston-is faster. It is a further advantage that no spring action is used for return stroke. We depend on differential air pressure effects. Moreover, we can arrange (as will be exemplified) that venting below the working piston precedesas a matter of phase-the effect 3,479,926 Patented Nov. 25, 1969 of working pressure, and this further contributes to fast action. Indeed by suitably arranging the phases of operation, a degree of air cushioning can be provided at the end of the working stroke, the rebound of which may accelerate the performance of a complete cycle.

The invention aims at improvements in such respects, and also has other advantages, which to those concerned In design and use will become apparent from the following description:

The invention resides primarily in an air gun tool of the kind referred to having the two ends of a doubleacting working piston and cylinder cooperating with axially-moving piston-valves the first one of which opens from the cylinder to admit compressed air to one side of the piston for the working stroke and is so opened by pressure-difference, the second one of which opens from the cylinder to vent air from the other side of the piston and is so opened by pressure-difference, the two valves being respectively closed to effect the return stroke by reversal of the pressure differences acting on them, a control valve to effect the reversal of the pressure differences, further valve means to vent the working air from acting on .the piston this further valve means being operated reversibly by pressure difference.

Further, the invention includes an air gun tool of the kind referred to having a double acting working piston in an open-ended cylinder, and a first and second piston valve respectively slidable in further cylinders which are arranged to close and open the ends of the open-ended cylinder under the influence of reversibly-applied air pressure. The invention includes such a tool in which the position of the working piston in its stroke, controls a valve which when open, admits air to act on the working piston for the return stroke thereof.

In a tool as above stated, it may be provided that a piston valve in its movement and as a function separate from its function as a main cylinder-valve controls venting from one or other side of the working piston.

Further, it provides a tool as stated above in which the first piston-valve carries a further pressure-operated valve which controls venting from one side of the working piston.

A tool having the foregoing features may be provided in which one (or both) of the piston-valves is so ported and ducted as to afford venting passage through the wall of the cylinder in which such valve slides.

The invention includes a tool as stated above, in which the pressure difference which operates the piston valves is controlled by a manually operated 2-way valve which, alternatively, admits compressed air to close the two piston valves or vents such valves for opening.

According to a collective or combination aspect of the present invention, the working piston operates, as a double-acting piston, in a working cylinder which is itself open-ended; this cylinder is closable at its upper end by a first piston-valve slidable in an upper valve cylinder and at its lower end by a second piston-valve slidable in a lower valve cylinder, these valves preferably seating on the respective ends of the working cylinder, and being opened and closed by the pressure of the supplied air; the working piston has a rod which is preferably the actual so-called blade of the tool, which slides through the second valve; a manually controlled valve controls the supply of air so that for the working stroke the first valve is opened to admit air above the working piston whilst the second valve is opened to vent air from below the working piston, whilst for the return stroke, air is vented from above the working piston and admitted below it.

The movement of the working piston itself, controls valve means involved in the working phase of the cycle, and the first piston-valve carries further valve means which operate (to vent) in the return phase,

A further feature of the invention resides in a particularly convenient arrangement of trigger-controlled valve, which will be seen to be embodied in one of the following examples. This arrangement is allied to a socalled bump fire device, by which the positioning of the tool on a workpiece causes the gun to operate (under the trigger control of the operator which over-rides it), and such that operation is automatically stopped if the tool is removed from the workpiece. This is so arranged, according to the invention, that either trigger control can be used or bump control. Yet another important feature resides in the provision of valve means operated directly in accordance with the position of the working piston, which enables the air space below that piston to be vented prior to the controlled admission of working pressure to that piston, so that no substantial pneumatic impediment to the working stroke can occur. This action may involve yet another feature, namely the provision of a holding device, preferably a permanent magnet or ball and spring latch arrangement of which there are many currently marketed, which retains the working piston in its extreme idle position, for a purpose which can be better understood from the second form of the first species described below.

The invention also includes a fastener air gun comprising a body housing a main cylinder which is open ended, double-acting main piston working in the main cylinder to perform the fastening operation, a cylinder head comprising a cylindrical boss extending from the body which supports it coaxially inwardly towards one end of the main cylinder said boss being of less diameter than the cylinder, amain valve cylinder formed in the body and coaxially surrounding the boss and of greater diameter than the main cylinder, an annular main valve member slidable in the main valve cylinder and slidable upon the boss, said member closing the corresponding end of the main cylinder in one external position and in the alternative extreme position defining an opening to the main cylinder of a cross-sectional air passage area so large as to give unimpeded access of air into and from said main cylinder, and valved duct means to subject said main valve member to opening and closing air pressures. In this aspect the invention also includes various subsidiary features which apply to the general feature, as well be defined in the claims.

The inventinon may be better understood from the following description of two constructions, given by way of examples, and with reference to the accompanying drawings, in which:

FIGURE 1 is a sectional view of a hand-held air gun, in the static condition;

FIGURE 2 is a section on the line IIII of FIGURE 1;

FIGURE 3 is a sectional view from the same aspect as FIGURE 1, showing the parts as they are at the end of the working stroke;

FIGURE 4 is a view similar to FIGURE 1 of a gun according to a variant of the species of the first example, in the static condition;

FIG. 5 illustrates the gun of FIGURE 4, at the end of working stroke;

FIGURE 6 illustrates the gun of FIGURES 4 and 5, with the working piston in an intermediate position in the return stroke;

FIGURE 7 is a sectional view on the line XX of FIGURE 4;

FIGURES 8, 9, 10, similarly illustrate a second (and simplified) species of gun, constructed according to the invention;

FIGURE 11 is a section on line YY thereof;

FIGURE 12 is a fragmentary sectional view of a modified construction of the working piston and the upper main valve member in the phase condition of FIGURE 10, namely in the return stroke; and

FIGURES 13, 14 15, illustrate a modification of the 4 gun of FIGURES 8-11, these three figures corresponding as to point of view and phases of operation.

In general, parts which are common to the examples of FIGURE 1 and of FIGURE 7 are given the same references, being readily recognisable. FIGURES 8-11 are, however, given new references. In FIGURES 13, l4, l5, insofar as identical parts are shown they have the same references as FIGURES 8-11.

In the illustrated examples, no parts are shown which are concerned with the fastener-feed magazine or the like which is often supplied as an adjunct to guns of this kind.

In FIGURES 17 the gun has a hollow body 1, with an integral hollow piston-grip 2 connectable to the compressed-air supply in known manner. The body and grip 1, 2, may be a light-metal die casting, or a synthetic resin moulding. The main part 1 is, internally, of generally cylindrical internal formation; it has, on a common axis, an upper cylindrical bore at 3, and a main cylindrical bore at 4. The bore at 3 is of slightly larger diameter than that at 4. In the bore 4 is supported, through three radially projecting legs or splines 5A, the working cylinder 5 which is enclosed within the bore 4 and spaced from it to form an air cavity 6 to open to the hollow interior of the grip 2. The cavity 6 is, at all times, charged with compressed air through the grip. The splines 5A are located fixedly to the body 1, thus the cylinder 5 is fixed in the body 1.

In the cylyinder 5 is the working piston 7. This is preferably of synthetic resin, and assembled to include a packing ring 7A. To it, coaxially, is attached a piston-rod in the form of the blade 8 of the machine, and the attachment is by a nut 9, so that different types of blade can be interchanged readily. Further reference to special features of the blade will be described later.

Slidable in the bore 3 and, with less diameter, in the bore 4 is the admission piston-valve 10, being a main valve member which again may be of synthetic resin, sealed in bore 3 (at greater diameter) by packing ring 10A, and in bore 4 (at smaller diameter) by packing ring 10B. A seal ring 10C in the under face of valve 10 is located to abut and seal against the upper rim of the cylinder 5 when the valve 10 is down (closed). The main valve 10 has a stepped edge, represented at 10D, surrounding the seat packing 100, so that the cavity 6 is in pressure communication to an annular underface of the valve, or relatively small area, at all times tending to move the valve 10 upwards. The seal at 10C (when valve 10 is down, i.e, closed) obviously cuts off pressure air in 6, from the working cylindrical space above the piston.

In the piston-valve 10 axially and centrally is a further valve arrangement. Within a valve pocket 11A is the mushroom-head of a servo valve 11, which has a valve stem 11B with a guide or pilot part 11C slidable in a bore, and on the upper end of the stern 11B is a piston 11F slidably sealed by ring 11E in a cylindrical bore 11D which opens above the piston-Valve 10, and of which piston 11F the upper area is greater than the effective area of the head 11. From between the head 11 and piston 11F, there is formed in the piston-valve 10, a duct 10F which is always in open communication with a vent 12A to atmosphere. It follows that when valve 11 is open, the pressure-space above piston 7 is vented, and that when the pressure in space 13A above the piston 11F suffices to hold valve 11 open this is the case. On the other hand if the pressure below the valve 11 exceeds that which exerts on top of piston 11F in 13A, valve 11 is closed. Valve 11 is open during return stroke of the tool and closed in the working stroke.

The upper end of the body 1 is closed by a cap 13 which, in effect, completes the body. The cap 13 is recessed at 13A centrally, opposite the bore 11D, and also has an annular perimetral recess at 13B into which a duct 1A leads. The duct 1A runs the length of the body 1, and is a permanently open communication between the space 13A above the valve 11, and a space 15 (revealed later) below the second piston-valve.

The lower end of the cylinder 5 defines between itself and the bore 4, an annular cylindrical space; in this is sealed slidably by an annular U-sectioned seal 14M a skirt 14A which is integral with the lower piston-valve 14. The main valve member 14, sealed as to its annular upper skirt edge by a packing ring 14B, slides in the lower part of the bore 4. The valve 14 has a buffer-pad 14C to cushion impact of the piston 7. It also has a seat seal 14D to abut and seal against the lower rim of cylinder 5. It further has a downwardly projecting cylindrical boss 14F, sealedly sliding in an axial bore in the bottom end of the body 1. Through the valve 14 and the boss 14F is a twodiameter axial bore, the upper (larger) part 146 allowing the conventional shoulder of the blade 8 to enter (see FIGURE 3) and the lower (lesser) part 14H of which is as close a fit as is practicable, around the blade. The lower part of the bore 14H is consequently, usually rectangular this being the usual sectional shape of the blade 8.

Radially through the wall of the boss 14F is a duct 14] leading out to the pressure space 15 below the valve 14. The inner end of duct 14] is a seat for a ball valve 16. A further duct 14K leads from the duct 14] (when valve 16 is open) to bore 14G.

The servo valve 16 is controlled mechanically by the blade 8. The blade has a longitudinal groove or fiat 8A into which the ball valve 16 drops when the blade is between its upper and lower positions; that is, during the working and return strokes, the valve 16 is open, but at the strokeends it is closed by riding out of the grooves 8A. On the side of the blade 8 opposite to the groove 8A is also a fiat or groove 8B of shorter length. This is merely a leak path and is not essential, especially if the blade has substantial leak clearance between itself and the bore 14H. Further leakage is to be effective, from the bore 146 to atmosphere. Beneath the grip 2 is a trigger control valve assembly, of which a body 20 is secured to 1 and 2. In a body 20 is partially rotatable, a manual control spindle valve 21, actuated by a trigger 22 against a spring (not shown). The valve 21 is formed with an arcuate passage 21A, which when the trigger 22 is idle (FIGURE 1) opens communication through a duct 20A leading from the interior of the grip 2 and when the trigger is operated (FIGURE 3) closes that communication. The passage 21A is always open to a duct 21B which communicates to the space 15. When the trigger is operated, the passage 21A opens communication between duct 21B and a venting duct 23, which is open to atmosphere. However, the exit of duct 23 to atmosphere may be controlled by the known kind of safety valve, usually having a tappet extending from the bottom of the gun body, which prevents operation unless the gun is actually in contact with the workpiece; such is known in the art as a bump fire device, and such as shown below in the second example.

It can now be seen that the duct 1A openly communicates between the space at 13B and above the valve 10, to the space 15 below the valve 14.

The operation of the tool is as follows. When idle (FIGURE 1) high pressure is in 2, 6, 13A, 13B (and the above-valve pressure space); in duct 1A; in 20A; 21A, 21B, and 15; and in 6. Pressure in 15 is cut off from the cylinder space below the working piston 7, and groove 14H, or clearance leakage, vents this space. The servo valve 11 is open (pushed down by the working pressure above 11C) and vents from above the piston 7, through 10F and 12A, to atmosphere. The whole area of main valve 10 is exposed to pressure (opposed only by the wall area at 10D) so valve 10 is pressed firmly against the top rim of cylinder 5, closed. Also, main valve 14 is pressed firmly against the bottom rim of cylinder 5'. Pressure in 6 exerts a control downward force on the annular area of the skirt 14A of the main valve 14, but this is not constantly a supervening force; it is however, such 6 a force as to open valve 14 when the pressure is vented from 15.

Now the trigger 22 is pulled, and the control valve 21 operates, to initiate the working stroke. By the valve 21, pressure is cut off from all ducts and chambers, except chamber 6; moreover, the other ducts and chambers are vented (through 218, 23) to atmosphere. The immediately effective pressure is therefore, that in 6 which acts upwardly on the peripheral area of main valve 10 (at 10D). Valve 10 is thereby lifted and opened, and due to the large port area now opened between valve 10 and upper rim of cylinder 5, the whole top area of the working piston 7 is exposed to the working pressure; servo valve 11 is closed by the pressure below it.

Pressure having been vented from space 15 below main valve 14, this valve is free to open the whole port area at the bottom rim of the cylinder 5, so the piston 7 is unimpeded in its working stroke.

Just after the blade 8 begins to descend, servo valve 16 is opened (by receding into the groove 8A). Duct 14K, being now open to 14] and through 15 to atmosphere, initiates the venting from below the piston 7.

However, further venting is opened when the servo valve 14 is dropped. This is because radial ports 14L in the skirt 14A, register with ports 1B in the wall of body 1.

When the trigger 22 is released, the general pressure pattern of FIGURE 1, described above, is reestablished but in addition, the servo valve 16 being open, pressure air enters the cylinder pressure space below the piston 7, and effects the return stroke; valve 10 is closed by downward pressure, but servo valve 11 is open (pressure difference across it being removed) so the space above piston 7 is vented.

As regards the variant of the foregoing example, reference is to FIGURES 4-7, in which similar parts have the same references. This example is of a gun having a bump firing deivce, a different trigger operated valve, and valve means which vent underside of the working-stroke in a phase of operation which precedes the working-stroke phase. In this example the end of the working stroke may be cushioned by air below the working piston. The example also includes a detent device which retains the working piston at the top of its stroke, to ensure stability of operation.

The main structural parts are generally the same as in the first example. The working piston 7 oscillates in the cylinder 5 and operates the blade 8, and there is a main body 1 with hollow pistol-grip 2, the body having the upper end cap 13 and air duct 1A. However, one minor modification can be seen in FIGURE 7, in that there are now four lands 5A defining the air passages 6 between the cylinder 5 and body 1. Again there is a main admission piston-valve 10 and lower main pistonvalve 14. The blade 8 no longer operates to control a valve by the groove system of the first example.

The modifications are incorporated to give more positive control over the movement of said upper and lower valves.

Driving power of the gun is improved by lowering the lower piston-valve 14 and thus venting the underside of the drive piston 7 to atmosphere prior to raising the upper valve 10 to connect the upper working chamber to air pressure. The new valve arrangements are included to automatically sequence such valve movements.

An additional valve 31) is included in the cap 13. Its purpose is to connect duct 1A to either pressure via chamber 13A or to exhaust chamber 13A via exit 31.

It works as follows. With chamber 13A connected to pressure, piston-valve 10 is forced downwards in an identical manner and performing an identical function to the earlier gun. Said pressure exerts a force on shoulder of a valve spool 30A forcing it downwards and thereby connecting duct 1A to chamber 13A via valve seating 30B. At the same time, sealing ring 30C, which is an integral part of valve spool 30, closes duct 1A from exhaust to atmosphere.

With duct 1A connected to pressure via valve 30 and chamber 13A said pressure is directed to chamber 15, thus lifting valve 14 to seal off lower face of cylinder 5 via contact with seal 14D.

Pressure in chamber 15 is also directed to underside of drive piston 7 through ducts 141 in valve 14. Pressure directed into underside of piston 7 will obviously lift piston 7 together with driver blade 8 until it is arrested by contact with a small protruding nose 30D of valve 30.

As the force acting on underside of piston 7 is larger than the force acting on face 30A, the valve 30 is lifted sufficient to break sealing face between seal 30E. This allows air from chamber 13A to travel via duct 10E to the underside of valve 30. Said air lifts 30 towards its up position. In so doing it seals off entry of further pressure from chamber 13A by valve seat 30B. Further slight movement upwards of valve 30 exhausts duct 1A and chamber 15 to atmosphere via seal 30C. The drive piston 7 and valve 30 will remain in this upward position due to air pressure being maintained via duct 10E below valve 30 and to piston 7 on the completion of its upward stroke contacting permanent magnet 40 or mechanical latch (of which an example is shown in the FIGURES 8-11 example and detailed in FIGURE 12), this maintaining the status quo. The magnet or latch 40 is mounted in the piston-valve 10 and coacts with a steel washer beneath the nut 9; this magnetic device thus acts as a detent, catching piston 7 at the top of its stroke and holding it with suflicient force to prevent any unstable rebound, and also ensuring that the piston does not move down under too small a pressure.

With chamber 15 exhausted to atmosphere via duct 1A and seal 30C, constant pressure from chamber 6 exerted on seal 14M and skirt section of valve 14 forces valve 14 downwards and connects underside of working piston 7 to atmosphere ready for another Working cycle.

Valve 30 will remain in the up position until the gun is next fired. At this time chamber 13A is relieved of air and so removing pressure from below valve 30 via duct 10E. With pressure removed from chamber 13A air below valve 10 lifts same to its up position as shown in FIG- URE 5 thereby remaking the seal between underside of valve 30 and seal 30E. By this means further entry of air via duct 10E is prevented when chamber 13A is reconnected to pressure.

Included with this variant of the gun is a device for providing for automatic bump control and working in the following manner.

It consists of a hollow rod 35, sealed at one end 35A. The rod is lifted by trigger 35B which in so doing seals further entry of air into chamber 13A by sealing at 35C. Slight additional lift of rod 35 breaks seal 35D and allows trapped air in chamber 13A to exhaust down a bore 35E in rod 35.

At the lower end of the rod bore 35E is a cross duct 35F, which connects with a duct 36 in the body. Duct 36 connects with a further duct 37 in which a valve 37A operates. Valve 37A carries a sealing ring 37B, which is in turn operated by an externally projecting bump nose 37E, which is lifted by the contact of the gun against the workpiece to provide a safety mechanism and bump control.

With the gun off the workpiece, valve 37 is normally in the down position due to pressure from chamber 2A acting on valve face 37C. In this position, air from space 2A is also connected to chamber 13A which is in turn connected via outside flats cut on the outside of valve 35 at 35G.

Raising the trigger 35B, as previously stated, seals off air entering chamber 13A via valve seating 35C. Now lifting the valve 37A until seal 37B is moved above duct 36 would seal ofi? any further entry of pressure via upper portion of duct 37D. It will at the same time allow pressure trapped in chamber 13A to escape via seal 35D and hollow section 35E via cross-hole 35F and duct .36 through duct 37 to atmosphere. This exhausting of chamber 13A will obviously fire the gun, since it allows the piston-valve 10 to rise.

It will now be understood that the gun cannot be fired without lifting valve 37 and exhausting chamber 13A via valve seating 37B. By providing suitable means for the lifting of valve 37 by contact with the workpiece an adequate safety mechanism is provided quite cheaply. Alternatively, with valve 37A locked in an upward position, the gun can be fired by contact of the trigger 35B only; so I may provide a removable locking pin or other retaining means to hold valve 37 in its up position, for example when single shots under trigger control are required.

Alternatively, a third method can be supplied; by leaving valve 35 upwards in the fire position and providing suitable means (e.g. nose 37E) of raising valve 37 by contact with the workpiece, the gun can be fired and re-cocked merely by contact with the workpiece; that is to say, reconnecting pressure to chamber 13A can be accomplished via duct 37D, duct 36 and the hollow stem of valve 35.

It will be noted also, especially by reference to FIG- URE 7, that in this example the cylinder 5 is located in the body 1 by four lands 5A. It is locked longitudinally by a circlip locking ring SE, to the ends of which (for fitting and removal) access by a tool is afforded through one of the four arcuate spaces between the lands 5A.

Where parts are provided for location in bores but required to pass air, they are of star or like fluted section; thus for example, a guide part is shown just above the nose 37E and although not so drawn, it is longitudinally fluted; and similarly the rod 35 is externally fluted along its upper part (that is from 35C up to 35D), to aflord air passage.

FIGURES 8, 9, 10, and 11 illustrate the second species of the invention, which is in some respects simpler than the first. This form will be seen to embody some of the features of the two previous constructions and to omit others. In this case, a new set of references will be used.

The main structure is an outer body 101 with a laterally extending pistol-grip 102 these collectively being hollow and permanently charged with pressure air when the gun is in use, in their cavity 103. Supported in the body 101 by radial webs 104 is the main working cylinder 105, the bottom rim of which is sealed at 106 to the outer body. The bottom of the body 101 has an integral closure, and the top is closed by a cap or head 107, in which is formed a cylinder and some ducting referred to later.

In the cylinder slides the working piston 108 to which is attached the blade 109 which has a longitudinal groove or flat throughout almost its whole length, indicated at 109A. At the very top of the blade 109, just be low the piston 108, the blade is of full cross-section, as indicated at 109B, this part having a valving function as will be seen. The blade 109 extends slidably through a passage in the bottom of the body 101.

The upper inner margin of the body 101, at 110, is formed cylindrically (coaxially with cylinder 105), the diameter of this formation being greater than the bore of cylinder 105. The cap 107 is formed with a further coaxial cylindrical interior holow, at 111, with a diameter larger than that at 110.

Slidable, and sealed by suitable rings, in the cylinders, 110, 111, is the upper main valve member 112. In its down or closed position (FIGURES 8 and 10) the valve 112 bears, sealed by a ring 113, against the upper margin 114 of the cylinder 105, projecting somewhat from cylinder 110. The edge of the valve 112 may be chamfered as at 112A, because air pressure is to act upwards on valve 112 on its area outside the seal ring 112A.

The main valve member 112 carries two servo valve arrangements in apertures which traverse it from top to bottom. The first of these is the centrally arranged mush room valve 113 seating upwards at 114 in the valve 112, and having a stem 115 connecting it with a piston 116 which slides in a cylinder 117 formed in the main valve. The main valve has radial ducts 118 leading from above the valve head 113 (and below the valve piston 116) to the perimeter of the main valve 112, above its less diameter and below its greater diameter, at which region an annular space 119 is left within cylinder 111. Exhaust ducts 120 lead from the space to atmosphere, through the cap 107.

In the lowest part of the passage in which is the valve 113, in an enlarged or widened part thereof at 121, is located in a groove a resilient circlip ring. On the crown of the working piston 108 is a peripherally grooved boss 122, which fits into and engages the circlip, this arrangement forming a detent which holds the piston 108 and valve member 112 in their respective uppermost and fully down positions, until a Sllfi'lClCIlt force operates them by breaking the detent. This arrangement fulfils substantially the same purpose as the magnetic detent arrangement of FIGURES 4-7.

Also supported in the main valve member 112 is a second servo valve, comprising two annular valve lands 123A, 123B carried on a stem 123, the ends of which stem (which as a whole slides in a valve bore through the valve member 112) are exposed to the pressures respectively above and below valve 112 whatever those pressures are according to the operative cycle: and the bottom end of which is abutted by the piston 108 when the latter is at the top of its stroke. The lands 123A, 123B act like a spool valve, and the annular space 123C between them is always open to a duct 118 and therefore to the space 119. In the valve member 112 there is also formed a radial duct 124 which is opened to space 1230 cap 107, when the main valve 112 is down (FIGURE 8 9) but cut off (as in FIGURE when this servo valve is down. The duct 124 registers with a duct 125 in the cap 107, when the main valve 112 is down (FIGURE 8 or 10). When the valve 112 is down and the servo valve is down, land 123B opens duct 124 to the space above the valve member 112. Thus in that situation-which corresponds to FIGURE 10duct 125 is open to the abovevalve space, in the cylinder 111.

The duct 125 is continued in the wall of the structure 101, by the duct 126 which runs down to the bottom of the structure. At its bottom end, duct 126 opens into a cylinder 127 formed in the bottom of the structure. In this cylinder 127 slides the lower main valve member 128, which is a piston-like valve, having a slight annular relief at 128C to ensure air getting in below it. The valve 128 is preferably made of somewhat elastomeric material such as oil-resistant rubber, because it is to afiord a cushioning etfect when the working piston 108 descends upon it. Moreover, such material affords good sealing in cylinder 127; and the edge of the valve is able (as is required) to seat sealedly against the lower rim 105B of the cylinder 105 when the valve 128 is in up position (as FIGURE 10). The valve member 128 is centrally axially apertured at 128A, for the blade 109 to slide freely through it, with considerable clearance to which the blade formation at 109A contributes, whilst the formation at 109B previously mentioned, fits into the aperture 128A to close it, as seen in FIGURE 9, when piston 108 is down and contacts valve 128. The valve member 128 also presents a boss, 1288, which projects somewhat into the confines of the cylinder 105 and provides more cushioning for the working piston 108.

The lower rim of the cylinder 105 has (say) four minor cylindrical bores formed through it, at 129, which would communicate from the cavity 103 to the seating where the valve member 128 abuts the cylinder rim. In each of these bores is a piston-like plunger 130, the function of which is permanently to urge the valve 128 downwards by reason of the air pressure in 103. The plungers 130 will there- 10 fore move the valve 128 down from the FIGURE 10 to the FIGURES 8, 9 position when pressure differences permit.

Below the rim of cylinder and through the wall of the structure, are radial exhaust ducts 131 which lead from above the valve 128 when the latter is down, (FIGURES 8 and 9) and are cut ofi by the closure of this valve when it is up.

In the root of the pistol-grip portion 102 is provided the operators trigger valve control. This has a finger-trigger 132 which bears upwards against a control valve 133 which is a spool-type valve with an outer sealed land 133A and an inner land 133B: these lands slide in sealed relation to internally-lodged seal rings, in the valve bore 133C. From the upper part of the bore 133 goes a duct 134 which runs up, through the wall 101 of the structure, through the cap 107 into the above-valve space of cylinder 111. This duct 134 is opened to the cavity 103 when the trigger 132 is not pulled, and is opened to a further duct 135 in the structure wall, when the trigger is pulled, simultaneously being cut off by the land 133A from the air supply, namely the cavity 103.

The duct 135 is provided to lead to a bump fire control if such be required, of which the operation is comparable to that described in the FIGURES 4-7 construction. If such a control is not required, the duct 135 is open to atmosphere.

The operation of the gun, in this example, is as follows. FIGURE 8 illustrates the static position, in which the gun is cocked ready for firing; FIGURE 9 illustrates it at the end of the firing stroke; in FIGURE 10, the working piston is on its way, returning from the FIGURE 9 to the FIGURE 8 position. FIGURE 11 is a section on these figures, on line YY of FIGURE 8.

In all these figures the cavity 103 is kept fully charged with pressure air. In the FIGURE 8 situation, duct 134 being open to cavity 103, loads the top chamber, above valve 112, with pressure air. This forces valve-piston 116 to open valve 113. Valve 112 is forced on its seat at 113. Ducts 118, 119, 120, are all open to atmosphere and, through valve 113, so is the space above the boss 122 and piston 108; boss 122 is detained in engagement with valve 112 by circlip 121. Trigger 132 is, of course, down and therefore control valve 133 is down. The working cylinder space below the piston 108 is open to atmosphere through the lower main valve spring and the ducts 131. Pins (under the pressure in cavity 103) are holding valve 128 down (i.e. open-: the relief space 128A is at atomspheric pressure, by reason that duct 126 is connected by duct 124 to duct 118. Control valve duct is at atmospheric pressure unless a bump control valve is fitted, in which case in the FIGURE 8 condition the duct would be charged with pressure air.

Now, assume the gun to be fired by the trigger 132, and the situation at the end of the firing stroke is (see FIG- URE 9) changed to the following. Raising the control valve 133 vents duct 134 to atmosphere through duct 135. Pressure above valve 112 is vented. Pressure air in cavity 103 acts beneath the valve 112 on its margin area, and raises valve 112, the detent with the piston 108 being broken. Valve 112 in opening, exposes the top or crown of piston 108 to the working pressure. Since the space below the piston 108 is freely vented, the piston and the blade 109 are forced down with very high acceleration, to do their work on the fastener. Meanwhile valve 123, being mechanically released downwards (by piston 108 retreating from it) is still in fact held up (as in FIGURE 9) by the pressure difference across valve 112. However, there is no longer pressure on the servo valve piston 116, and therefore the working pressure below valve 113 closes this valve, cutting off what would otherwise be a vent to atmosphere of the working air. Piston 108 hits the resilient boss 128B, and the blade formation 109B blocks the passage 108A.

Release of trigger 132 brings about the situation of FIGRUE 10. Control valve 133 (now down) opens worklug-pressure air again to duct 134 and this to the space about valve 112. Valve 113 is thereby opened and the working space between piston 108 and valve 112 is vented to atmosphere via 118, 119, and 120. Simultaneously, valve 123 is forced down by the pressure about it, and pressure air from above valve 112 now flows via 124, 125 to relief space 1280, and so to raise valve 128 so that it seats at 105B against the cylinder 105, overcoming the downward load of the pins 130 which even collectively is a relatively small force. Upward movement of the valve 128 start the piston 108 upwards, and the working pressure acting on the cross-sectional area of the blade formation at 109B separates the piston from the bottom valve 128, working air flows through 128, enters the lower cylinder space, and returns piston 108 (and the blade) upwards. Upon entering the recess in valve 112 the piston boss 122 is detained in valve 112 which is, of course, now in its down position. Simultaneously valve 123 is raised by contact with piston 108 and pressure air supply in duct 126 is thereby cut off, this duct and the spaces both above and below valve 128 being vented to atmosphere first by ducts 126, 124, 118, 119, and 120, and (once valve 128 has slightly dropped) by ducts 131.

It will be seen that the construction of the example of FIGURES 8-11 and its operation, are relatively simple, and it lends itself to light and easily fabricated components. The main components, such as the structure 101, cylinder 105, main valve 112 and piston 108 may either all or selectedly be made as plastic mouldings, reinforced as may be necessary. The valve 128 may be wholly of a somewhat elastomeric material such as fairly hard rubber, or it may be mainly of plastic with the boss 128B of fairly resilient rubber.

In FIGURE 12 sufiicient of the parts are referenced to identify them with parts in the FIGURES 8, 9, 10, 11 construction. In some cases, and especially when synthetic resin is largely used in the construction, it is deemed to be desirable to use a modified construction of working piston, upper main valve, and their coacting detent parts. This also facilitates interchanging blades.

In this modification the working piston indicated at large at 108, is built up of an under part 150 through a central hole in which lies the blade 109 and which has a marginal recess to receive an O-ring 152 or like slidable seal. Completing the piston, the upper or crown part 151 is secured thereto by grub-screws one of which is shown at 153, the ring 152 being thus held or nipped in position. The crown part 151 secures beneath it a conical head 154 formed at the end of the blade 109. Centrally in the crown part 151 is a circular hole 155, in the wall of which is an annular recess housing a springy ring at 156.

The upper main valve 112 has a circular recess formed in its under face, in which is located a disc-like part 157, secured by grub-screws as at 158. The part 157 has an axial bore 159 corresponding to and continuing the housing of the valve 113; this bore extends in a short circular-sectioned boss 160 which projects downwardly from and integrally with the part 157. The outside of the boss 160 has a slightly projecting bead or lip at 161, designed to engage in the spring ring 156; the bead and spring ring thus constitute a detent, equivalent to that which is seen in (e.g.) FIGURE 8.

The crown 151 and the part 157 may be made of material different from that of the main portion 150 Of the piston 108 and of the valve 112. For example they may be of steel, the other parts being of synthetic resin. It will be appreciated then, that the impact force in the blade 109 (i.e., on the head 154) is transmitted directly from the crown 151 upon which the air pressure operates, and the detent parts can be of adequate hardness and durability.

Evidently, the device is open to wide structural and detail variation. A feature of the invention in both species, is the provision with a double-acting air returned working piston, of the two main valves and the secondary or servo valve arrangements which enables them to act in the way described.

FIGURES 13, 14 and 15 illustrate a modification ot' the species of gun illustrated in FIGURES 8 to 12, in corresponding phases of operation. Much of the construction is the same, sufiicient references being shown to identify these.

In this construction, the upper main valve and associated parts are substantially modified. The cylinder head or cap 200 has an inwardly (downwardly) extending cylindrical boss 201 which has a central axial valve bore 202 in which slides a spool valve 203 with three ringsealed lands 203A, 203B, 203C spacedly formed thereon and fitting in the bore 202 and a frustoconical or mushroom valve head 203D which can seat on a complementary conically formed seat in an annular end plate 204 which is attached by suitable means to the boss 201; an extension stem 203E of the spool valve, extends through the plate 204, sealed by a ring 205. The stem 203E constitutes a tappet or striker against which abuts the head 154 of the blade 109 when the working piston 108 is in its up or static position (that is, when the gun is idle). This abutment holds the spool valve in up position.

The main valve member is, in this variant, an annular element generally indicated at 206. This member 206 has an inner bore 206A fitting around the boss 201 and sealed therewith by the suitably disposed O-rings illustrated. The diameter of the boss 201 (and therefore of the bore 206A) is equal to that of the working piston 108.

The valve member 206 has, as to its upper part, a large external diameter and its lower part a lesser external diameter, these being illustrated at 206B and 206C. The member thus has the characteristics of a differentialarea piston. The lower edge of the member 206, as shown at 206D, is narrowed to an annular flat end adapted to seat sealedly on the end of the main cylinder (as is seen in FIGURES 13 and 15). Preferably the member 206 is made of synthetic plastic and this is convenient in that it enhances sealingly.

The valve member 206 has seal rings around its largerdiameter part, at 206E and 206E; these allow the valve to slide sealingly in a complementary bore in the cap 200. A seal ring 2066 similarly seals against a lesser bore 207 formed in the body 101.

It is here mentioned that the plate 204 and the piston crown 151 have again the detent arrangement of FIG- URES 8-12. Moreover in the example, the crown 151 rises (when piston 108 is up) proud of the cylinder 105 and it is arranged so that it enters the lower skirt of the valve member 206 i.e. it extends a short way into the bore 206A.

The air passages in this case are as follows. Duct 134 (from the trigger valve) leads to the annular space 210 in the cap 200 which is above the main valve 206 when this valve is not fully up. When the valve 206 is down, space 210 opens via duct 210A to the annular spool-valve space between lands 203A and 203B. A duct 211 is always open, through the boss 201 and plate 204, between the main cylinder upper space and the space within bore 202 above the spool valve 203.

Ducts 212 lead from bore 202 to connect with a transfer duct 213 via an annular groove around the boss 201 (the duct 213 being through the valve 206) this connection occurring when the valve 206 is down (FIGURES 13 and 15 In the down condition, transfer duct 213 opens to the duct 126. A further duct 214 from bore 202 leads from bore 202 to the main cylinder upper space at 215; the boss 201 is tapered off towards its lower end as seen in the figures, to form this positively open space even when the piston 108 is up. It will be noted (see FIGURES 13 and that the space 215 is closed by the crown of the piston 108 when the piston is up and the valve is down. Finally, transfer ducts 216 through the lesser-diameter wall of member 206 connect space 215 to atmosphere via parts 217 and the body 101 when the valve is down.

The operative cycle is effected as follows.

Starting from the situation of FIGURE 13, the gun eing charged with pressure air through the grip 102, the

trigger 132 is pulled. Space 210 exhausts to atmosphere via 134, 135. The pressure on the lower edge of the valve member 206 is now unbalanced so the valve is sharply lifted. The seating at 206D now being opened and the edge of the piston crown 151 having left the bore 206A, the full area of the piston 108 is exposed to pressure and the working stroke is effected, the detent engagement being broken. When piston 108 retires from the spool valve 203, the pressure (through 211) forces the spool down, setting up the situation of FIGURE 14.

Relaxing the trigger 132 sets up the situation as illustrated in FIGURE 15. Now the bottom valve 128 is closed by pressure beneath it and leakage (through 128A) admits pressure air below piston 108, lifting it through its return idle stroke. The upper cylinder space exhausts to atmosphere via 216 and 217; spool 203 is relieved of pressure and is free to be raised by abutment of piston 108. The pressure from 134 moves valve member 206 down, and the situation of FIGURE 13 is thus restored when the spool 203 is moved up.

This construction, whilst being akin to that of FIG- URES 8-12, has the advantage that the pressure spaces which need to be charged or exhausted are much reduced so that air consumption is reduced. The valve member 206 is much lighter than the main valve member 112. A complete valve unit is dispensed with (that is, the functions of 115 and 123 of the earlier figures are performed by the valve 203 in conjunction with the other motions). The feature that the piston 108 cooperates directly with the valve 206 by the overlap referred to, is of merit because it enhances the suddenness of the application of pressure on the working piston. This feature also allows the working piston a slightly longer stroke (for given other dimensions of the gun) and this is in itself an advantage in terms of performance.

In this last example, it is almost unnecessary to mention that the duct 135 may, again, be connected to a bump valve control.

A large part of the gun so described can be made of synthetic plastic, but certain parts for example the plate 204- and crown 151 and the blade 109, would seem to be better made of tough and hard material such as steel.

I claim:

1. Fastener air gun comprising:

a body housing a main cylinder which is open-ended,

a double-acting main piston working in the main cylinder to perform the fastening operation,

a first main valve member at one end of said cylinder and of effective cross-sectional area at least equal to that of the main piston and slidable in said body to open and close substantially the whole sectional area of the cylinder, and

a second main valve member of like cross-sectional area at the other end of said cylinder and slidable in said body to open and close substantially the whole sectional area of the cylinder.

2. Gun according to claim 1 in which said first main valve member carries first servo-valve means to control air flow from or to one side of said first main valve member and is actuated directly mechanically by said main piston during part of the stroke thereof.

3. Gun according to claim 2 in which said first main valve member carries second servo-valve means to control air fiow from or to one side of said main valve member said second servo-valve means comprising a piston operating in a cylinder formed in said first main valve member and moving said servo-valve means in accordance with pressure difference across such piston.

4. Fastener air gun comprising:

a body housing a main cylinder which is open-ended and enclosing separately from the cylinder a hollow cavity for air, the body also defining a first and a second valve cylinder on an axis common with the main cylinder,

a double-acting main piston Working in the main cylinder to perform the fastening operation,

a first main valve member at one end of said main cylinder slidable in the first valve cylinder to open and close substantially the whole sectional area of the main cylinder, and

a second main valve member at the other end of said main cylinder slidable in the second valve cylinder to open and close substantially the whole sectional area of the main cylinder.

5. Gun according to claim 4 in which each said main valve member is itself a double-acting piston having in operation the character of a differential-area piston.

6. Gun according to claim 5 in which a main valve member has two different effective external diameters, and the valve cylinder corresponding thereto has two correspondingly different effective internal bore diameters.

7. Gun according to claim 4 in which the first main valve member carries a first servo-valve element slidable in the first main valve member in axial direction with respect thereto and adapted to contact mechanically with and thus be movable by the main piston.

8. Gun according to claim 4 in which the first main valve member carries a second servo-valve element slidable in the first main valve member in axial direction with respect thereto and adapted to be operatively moved by pressure differences across said first main valve member.

9. Gun according to claim 1, provided with detent means engageable between the working piston and the first main valve member so as to detain these together until detachament by the application between them of a certain air pressure.

10. Gun according to claim 9 in which said detent means comprises a springy ring and a complementary groove.

11. Gun according to claim 9 in Which said detent means comprise a permanent magnet.

12. Gun according to claim 1 in which both main valve members seat against a respective end of the main cylinder and both operate slidably in a cylinder of a bore larger than the main cylinder the difference of areas exposable to air pressure so defined being such as to operate the valve members.

13. Gun according to claim 1 in which the second main valve member is provided with a resilient part adapted to be contacted by the main piston towards and at the end of its working stroke whereby said second main valve member buffers the deceleration of the main piston and the second valve member in closing can assist the acceleration of the main piston in its return stroke.

14. Gun according to claim 1 provided with a manually operable trigger control and a bump control, and valve means operable by these to control the supply or release of pressure air to actuate the main valve members in the cycle of opening and closing required to expose one or other side of the main piston to pressure respectively for the working or return stroke.

15. A gun according to claim 4, in which said first main valve member in its sliding movements opens and closes air ducts between itself and the first valve cylinder.

16. Gun according to claim 4 in which the first valve member seats with one of its ends on an end of the main cylinder around an effective area which is less than the total effective area of the member whilst its other side is always exposed over its total area.

17. Gun according to claim 1 in which the second valve member has minor pistons associated therewith and adapted to be connected to a source of air pressure for urging said second valve member towards opening when it is closed.

18. Gun according to claim 1 in which said gun has a gun blade and the second valve member has a substantially central axial passage through which said gun blade is slidable, has air ducting for effecting the operation of the gun, and has valve means for controlling said ducting in accordance with the sliding of said blade.

19. Fastener air gun comprising:

a body housing a main cylinder which is open-ended,

a double-acting main piston working in the main cylinder to perform the fastening operation,

a first main valve member at one end of said cylinder,

a second main valve member at the other end of said cylinder,

each of said valve members being slidable in said body and having means for seating the valve member against the corresponding cylinder end and alternatively for permitting the valve member to open substantially the entire circumference of the corresponding cylinder end and provide substantially unimpeded access of air into and from said cylinder.

20. Fastener air gun comprising:

a body housing a main cylinder which is open-ended and defining first and second valve cylinders substantially coaxially with the main cylinder at opposite ends thereof,

a double-acting main piston working in the main cylinder to perform the fastening operation,

a first main valve member at one end of said main cylinder slidable in the first valve cylinder to open and close substantially the whole circumference of the corresponding end of the main cylinder, and

a second main valve member at the other end of said main cylinder slidable in the second valve cylinder to open and close substantially the whole circumference of the corresponding end of the main cylinder.

21. Gun according to claim 20 in which each of said main valve members has means for seating the valve member against the corresponding cylinder end and alternatively providing substantially unimpeded access of air into and from said main cylinder.

22. Gun according to claim 20 in which said body has a cylindrical boss extending coaxially inwardly toward said one end of said main cylinder, said first valve cylinder coaxially surrounding the boss, said first main valve member being annular and slidable in the first valve cylinder upon the boss, said first main valve member closing the corresponding end of the main cylinder in one extreme position and in the alternative extreme position de fining an opening to the main cylinder of a cross-sectional air passage area so large as to give unimpeded access of air into and from said main cylinder, and valved duct means to subject said first main valve member to opening and closing air pressures.

23. Gun according to claim 22, in which said first valve cylinder is of greater diameter than the main cylinder,

said boss is of diameter substantially the same as or slightly less than the main cylinder, and said annular valve member seats upon the corresponding end of the main cylinder.

24. Gun according to claim 23 in which said main piston protrudes from said one end of said main cylinder in its idle condition and said annular valve member also seats upon the protruding main piston.

25. Gun according to claim 22, further comprising a servo-valve slidable axially in said first boss and actuated by air pressure and by mechanical contact with the working piston.

26. Gun according to claim 22, in which the said first main valve member regarded as an annular piston, has two effective cross-sectional areas so as to operate as a differential piston.

27. Gun according to claim 21, in which the said first main valve member has a single-diameter internal bore sliding on the said boss and has two external diameters. the said first main valve cylinder having two corresponding bore diameters.

28. Gun according to claim 22 in which the said first main valve member has an internal bore complementary to and receiving the crown of the main piston in the idle position of the latter.

29. Gun according to claim 22 in which the said first main valve member seats against the end of the main cylinder in the idle position of the gun.

30. Gun according to claim 22 in which are provided force-releasable detent means engageable between the working piston and the said boss.

31. Gun according to claim 22 in which said first main valve member in its sliding movements opens and closes air ducts between itself, the said boss, and the said first main valve cylinder.

References Cited UNITED STATES PATENTS 2,944,522 7/1960 Doyle 227l30 2,979,725 4/1961 Wandel 227 2,983,922 5/1961 Juilfs 227l30 3,094,043 6/1963 Powers 9l4l6 3,188,921 6/1965 Bade 9l399 3,190,187 6/1965 Doyle 9l403 3,253,760 5/1966 Doyle 227-430 3,255,674 6/1966 Nelson 9146l 3,320,860 5/1967 Bade 227-130 3,352,471 11/1967 Fisher 227-130 833,090 10/1906 Shepherd 91-45l X 2,934,093 4/1960 Bleasdalc 92171 X 3,342,110 9/1967 Schafroth et a1. 91-454 CARROLL B. DORITY, ]R., Primary Examiner US. Cl. X.R. 

